R-M interactions in R2BaMO5 (R= Y,Gd and M=Cu, Zn).

G F GOYA; R.C. MERCADER; L B STEREN ; R D SÁNCHEZ ; M T CAUSA; M TOVAR++

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Año: 1996 vol. 8 p. 4529 - 4539

0953-8984

R2BaMO5 (R D Gd or Y; M D Cu or Zn) oxides have been studied using thespecific heat, DC magnetic susceptibility and electron paramagnetic resonsance (EPR). For onemember of the series without a magnetic moment at M, namely Gd2BaZnO5, measurementsreveal long-range antiferromagnetic order at TN.Gd2BaZnO5/ D 2:3  0:1 K, much lower thanthe Curie–Weiss temperature 2 of 15:9  0:3 K. This indicates the existence of competinginteractions that introduce a large degree of magnetic frustration in the system. For Y2BaCuO5the Cu–Cu interactions are responsible for the broad maximum in the magnetic contributionto the specific heat centred at 18:5  0:01 K that stretches beyond the instrumental limit of25 K. The strong Cu–Cu interactions also present in Gd2BaCuO5, combined with the Gd–Cuinteraction, polarize the Gd sublattice, giving measurable contributions to the specific heat in thesame temperature range. In addition, they broaden the Gd EPR line and saturate its integratedintensity. The ordering temperature of Gd ions is raised to TN.Gd2BaCuO5/ D 12:0  0:1 K.